Caller ID is a telephone on-hook capability that provides a called party with information about the caller before the incoming call is answered. Conventionally, such information includes the date and time of the call and the caller's telephone number. A data message, preceded by a channel seizure signal, is sent in conjunction with the ringing signal from the central office to the called party during the silent interval after the first 20-Hz, 2-second ringing phase.
Caller ID service is designed for use with the voice portion of existing loop connections. The digitally formatted message is transmitted through a stream of data bits of standardized digital format. The message is sent once, without retransmission capability. The channel seizure signal, sent at the beginning of each message to alert the called party equipment of the coming information through physical connection of an appropriate interface, is typically composed of thirty continuous bytes of octal 125 (i.e., 01010101), or 250 milliseconds of a 600-Hz square wave. Transmission of data follows thereafter and is completed prior to the next 20-Hz ringing signal. For a detailed description of the method and apparatus for sending the data message, reference is made to U.S. Pat. No. 4,551,581 issued to Doughty on Nov. 5, 1985.
The receiving display apparatus at a caller ID subscriber location may be as disclosed in U.S. Pat. No. 4,582,956, issued Apr. 15, 1986. The apparatus, which may be a part of a telephone instrument or a stand-alone device, includes a line interface unit, a converter, a control circuit and a display unit. A frequency shift keyed (FSK) signal representing the special service information is filtered from the ringing signals by the line interface unit. The converter detects the FSK signal and demodulates the special service information from the FSK signal. Following detection of the FSK signal, the control circuit receives and stores the special service information. The stored information is periodically sent to the display unit to begin exhibiting thereof during the silent interval before the next ringing signal.
The caller ID service in the public switched telephone network (PSTN) offers several advantages to the called party subscriber. Identification of the calling party, as provided by the caller ID service, allows the called party to screen an incoming call personally before its completion and thereby to decide whether or not it is desirable to answer the call. Nuisance calls, such as advertising and solicitation calls, can be avoided if the identity of a caller can determined before a call is answered. Knowledge of caller identity also serves as a resource for dealing with and curtailing harassment calls.
Reference is made to U.S. Pat. No. 5,497,414, issued to Bartholomew on Mar. 5, 1996, for a discussion of the advantages to the called party subscriber as well as the countervailing disadvantageous effects on the caller's privacy. If the caller number identity is made known to a called party caller ID subscriber each time a call is made, the privacy afforded to a caller having an unlisted number is significantly compromised. Similarly, any caller may find it desirable to place a call without revealing origination identity to the called party. In such case, the caller must take the risk that the called party line does not subscribe to the caller ID service.
As a recourse, the caller in some existing systems is given the option to block transmission of caller line origination identity to the called party. If the called party is a caller ID service subscriber, the display unit will either indicate a caller privacy condition or remain blank. Reference is made to U.S. Pat. No. 5,161,181, issued to Zwick on Nov. 3, 1992, for discussion of this concept. With caller ID blocked, a call is directed to the called party for completion in the standard manner and the functionality of caller ID is lost, along with its advantages to the called party subscriber. The caller can thus retain anonymity with an increased likelihood that the called party will elect not to answer the call.
Accommodating the requirements of called party subscribers to screen the origination of incoming calls before answering, while permitting calling subscribers to individually control what origination information will be transmitted for placed calls, is an ongoing concern of service providers. Enhancements to the basic caller ID service have further complicated these considerations.
With one such enhancement the network provides the caller's name as well as the caller's number for display at the caller ID box of the called party. The phrase "enhanced service" as used herein refers to the capability of supplying both text and telephone caller number identification information. A caller who blocks caller ID to avoid a return call from the called party may find benefit in transmitting the name information alone for identification purposes. Conventionally, the ability to transmit name information without originating telephone number information is not available. Moreover, the provision of additional caller ID information increases the risk that misleading information will be transmitted. For example, a call may be placed from a subscriber location at which several people reside. If the caller is not the listed subscriber, the called party may not recognize the identified caller name and choose not to answer the call. Identification of the name of the actual caller instead of the name of the subscriber is a function that prior art telephone systems lack. Such a function would be a benefit both to the called party, who may know the called party and thus answer the call, and the calling party who is more likely to have the call completed.
Complications also arise with callers that subscribe to distinctive ringing type services that provide a plurality of telephone numbers for the same subscriber line. The distinctive ringing service subscriber may reserve one number for important calls, which would be answered under most circumstances, while using another number for less important calls that the subscriber may choose to ignore. Alternatively, each number may be associated with a different resident, the intended called party being indicated by the distinctive ring. In other circumstances a subscriber may require two telephone numbers for a single line to distinguish between business calls and personal calls. The business name would be listed for the business number, while the subscriber's name would be listed for the personal use number.
Conventionally, one of the listings for the multiple number line is recognized as a primary listing, the remainder as secondary listing(s). A called party subscriber to the basic caller ID service would receive from a multiple line calling subscriber a display of the caller's primary telephone number. A called party subscriber to the enhanced caller ID service would additionally have displayed the primary name associated with the primary number. The calling party may not wish to transmit the primary number and its associated listed name for a particular call. Depending upon the purpose of the call, a secondary number listing may be appropriate. A similar situation exists with a business subscriber who has a plurality of stations, each with a direct dial number. A caller from one of the stations may wish to select among several numbers to be displayed to the called party.
The above-identified application, Ser. No. 08/725,349, describes a system and method for distinguishing between numbers, as well as names, in the transmission of caller identification information for an individual call. The advanced intelligent network (AIN) is used to allow a calling party to specify what caller ID information to send to the called party for display. The telephone system Line Identification Data Base (LIDB) contains listings for subscribers that may each include a plurality of assigned telephone numbers and names. On an individual call basis, a calling subscriber can control what information is to be extracted from LIDB for identification to the called party. Various identification options may be pre-established, the caller invoking a selected option by dialing a corresponding access code with the dialed telephone number.
The system described above affords great flexibility to calling parties while safeguarding the interests of called parties to receive accurate information. These advantages are attributable to a large extent to the fact that the calling party identifying information, while conforming to a caller's preselected desired design, is generated by the network. As the information is prestored in a data base, called parties can be safeguarded against receipt of inappropriate information. The accuracy of the caller's identifying information can be verified upon storage by the system prior to transmission in telephone calls. Such verification need be done only when new identifying information is entered into the data base, as only the verified information can be transmitted thereafter. A called party thus has a reasonable expectancy that the received calling party information is reliable.
This safeguard of the above described system, however, is not available for calls placed from a PBX system, which can generate calling party information data at the discretion of the private administrator, or an acting individual, on a call by call basis to be transmitted via a PBX trunk to its associated PSTN switching facility. A calling party from the PBX system can simply dial out the called party number without need for an access code as the desired calling party information can be programmed at the PBX. With such on premises control, there is no need for the PBX customer to subscriber to the LIDB access selective caller ID service. The calling party can thus output erroneous text information as well as indicate an inaccurate and unverified calling party number. The receiver of such call, upon returning the call, may unintentionally reach a third party instead of the actual calling party, to the annoyance of both the returning caller and the third party. This nuisance can also exist for called parties who do not subscribe to caller ID services but invoke a "return call" service.
The need therefore exists in the prior art for system authentication of calling party identification information generated from PBX systems. Such a provision would prevent fraudulent use of third party information as well as avoid common mistakes in entry of data in PBX systems. Caller ID information authentication is of even greater complexity for interLATA calls in which several transmission carriers, including interexchange carriers, are involved. U.S. Pat. No. 5,530,741, issued to Rubin on Jun. 25, 1996, discloses a system wherein the interexchange carrier controls provision of calling party number. Authentication by the called party's local exchange carrier is thus dependent upon information under the control of other carrier(s).